In accordance with recent technical development, portable computers that are compact, light and easy to carry have been produced and are available on the market. FIG. 20 is an outline diagram of a common portable computer (IBM ThinkPad 560 ("ThinkPad" is a trademark of IBM Corp.)). The computer includes a main body on which a keyboard unit is mounted, and a cover unit in which a liquid crystal display is provided. That is the portable computer has a clam shell structure where the cover unit is pivotaly hinged on the almost rear edge of the main body. The portable computer has, for example, an A4 or a B5 footprint, and weighs 2 kilo grams or less, and can be fit into a bag for carrying.
In accordance with the expanding needs of users, various forms of portable computers have been manufactured. Some portable computers have been designed that provide an input tablet on a liquid crystal display to enable pen input. A portable, tablet input type computer is disclosed in, for example, Japanese Patent Application No. Hei 4-301950 (Japanese Unexamined Patent Publication No. Hei 6-202806) which is assigned to the present assignee.
For the portable, tablet input type computer (hereinafter referred to as a "tablet computer"), as input means, a tablet replaces a keyboard. Therefore, a common tablet type computer, which has a flat, plane box shaped main body, does not have keyboards as standard equipment, and has a tablet that also serve as displays provided on their fronts. While an operator is looking at a tablet display of a tablet computer, the operator indicates a desired position by using a pen, instead of inputting at a desired key, to input data or commands.
The manner in which clam shell type portable computers are used is standardized. More specifically, when this type of computer is not being used, such as when it is being transported, the cover unit is closed to hide and protect the liquid crystal display and the keyboard surface which are relatively easily damaged by mechanical impact. When the computer is to be used, the main body is placed on the flat surface of a desk, or on a lap, and the cover unit is opened to permit viewing of the display and manipulation of the keyboard.
On the other hand, the manner in which the tablet computers are used is not always standardized. For a tablet computer, a pen may be used for data input, or an external keyboard unit may be attached for data input using keys. In the latter case, the tablet is used only as a display. The pen input operation may be performed on a desk, or by holding the pen in one hand and supporting the computer with the other hand. Pen input operation is relatively easy with a tablet computer having a main body in a flat, plane box shape when the computer is placed flat on a desk Because an operator can manipulate a pen while looking down at the tablet display. However, for data input using an external keyboard, an operator must view a display, lying flat on a desk, at an acute angle, and this arrangement makes the operation difficult. Especially for a display that has a narrow visual angle, an operator is forced to take an unnatural posture in order to perform key input while viewing the display.
In addition, even for performing pen input on a desk, it is evident that, from the aspect of human engineering, an input face that is slightly inclined toward an operator provides better usability than does a flat input face.
In short, the conventional tablet computer having a main body in a flat, plane box shape is satisfactory only for pen input on a desk, and is not suitable when used in other ways.
Various "tilting mechanisms" for inclining a keyboard toward the front relative to a horizontal face have been proposed for the conventional clam shell portable computers. In, for example, the specification for Japanese Patent Application No. Hei 3-290406 (Japanese Unexamined Patent Publication No. Hei 5-119885) is disclosed a tilting mechanism constituted by a pair of folding stand provided on the bottom of a portable computer. Such a tilting mechanism effectively enhances the usability for key input. The tilting mechanisms, however, generally have a single tilting angle, and are not satisfactory for use when a computer is supported by one hand and a pen is held in the other hand. The tilting mechanisms were originally provided to incline the typing face of the keyboard, not for providing an enhanced tablet data input operation. When a tablet is used as a display that is inclined at only a small angle by the folding stand, it is difficult for an operator to see the display- In order to make the above described inventions suitable for the other applications, such as for tablet input, or for use as a display, it is desirable that different types of stands having different lengths be prepared.
It is, therefore, one object of the present invention to provide a superior tablet type information processing apparatus having a main body in a flat, plane box shape.
It is another object of the present invention to provide an improved information processing apparatus that can also be appropriately employed in several ways, such as for tablet input or for key input with a keyboard.